To date, there has been no report on the pharmacological, biological activities of quercetin-7-rhamnoside. However, the pharmacological activities of the flavonoids or glycosylated flavonoid s having similar structures of the quercetin-7-rhamnoside have been widely known [Journal of Antimicrobial Chemotherapy, L. C. Chiang, W. Chiang, M. C. Liu and C. C. Lin, Vol. 52(pp 194˜198), 2003]. Although there are reports that flavonoids have an antiviral activity against herpesvirus, adenovirus, etc. and that such biflavonoid compounds as robustaflavone have an inhibitory activity against influenza virus, etc. [Planta Medica, Yuh-Meei Lin, Vol. 65(pp 120˜125)], these antiviral activities do not appear to be excellent.
The present inventors have already shown that the Houttuynia cordata extract has antiviral activity against coronavirus [Korean Patent Application No. 2004-97587] and succeeded in isolating the active ingredient from the Houttuynia cordata extract, which was identified as quercetin-7-rhamnoside. Korean Patent Application No. 2004-97587 filed by the present inventors discloses the antiviral activity of the Houttuynia cordata extract against coronavirus. But, they completed the present invention by confirming that the quercetin-7-rhamnoside has an antiviral activity against coronavirus 700 times superior to that of the Houttuynia cordata methanol extract, as well as superior antiviral activity against influenza virus.
Thus, an object of the present invention is to provide an antiviral composition comprising quercetin-7-rhamnoside, a derivative thereof or a pharmaceutically acceptable salt thereof as an active ingredient.
Another object of the present invention is to provide a method for isolating quercetin-7-rhamnoside from the Houttuynia cordata extract.